1. Field of the Invention
The present invention relates to a resist peeling system and a control method of a resist peeling solution, and particularly to a resist peeling system used for peeling resist residue on a semiconductor wafer, and a control method for suitably controlling the state of the resist peeling solution.
2. Description of the Background Art
In the process for fabricating semiconductor integrated circuits, a treatment for removing resist residue remaining on a semiconductor wafer, that is, a resist peeling treatment is performed after dry etching for forming interconnections and holes. In the resist peeling treatment, a resist peeling solution containing organic amine and the like cleans the semiconductor wafer.
The components ratio in a resist peeling solution changes with time. In particular, the components ratio in an amine based peeling solution that is common as a resist peeling solution is apt to change significantly, since it is used under a high temperature environment. The change in components ratio in the resist peeling solution may cause an inconvenience that interconnections on a wafer are excessively etched with the resist peeling solution or the residue removing ability of the resist peeling solution is degraded.
To solve such an inconvenience, in the process of fabricating a semiconductor integrated circuit, a manner of periodically exchanging a resist peeling solution is generally adopted; however, such an exchange of the resist peeling solution results in increased production costs of semiconductor integrated circuits. Accordingly, in order to reduce the production costs of semiconductor integrated circuits, it is essential to reduce the cost of the resist peeling solution, and more concretely, to prolong the service life of the resist peeling solution.
The present invention has been implemented in order to solve the above-described problems, and a first object of the present invention is to provide a resist peeling system capable of prolonging the service life of a resist peeling solution by keeping the components ratio in the same in a suitable range.
A second object of the present invention is to provide a method of controlling a resist peeling solution, which method is capable of prolonging the service life of a resist peeling solution by keeping the components ratio in the same in a suitable range.
The above objects of the present invention are achieved by a resist peeling system for peeling resist residue adhering on a semiconductor wafer by using a resist peeling solution composed of multiple components. The resist peeling system includes a peeling solution tank for storing the resist peeling solution as well as an electric conductivity monitor for monitoring the electric conductivity of the resist peeling solution. The resist peeling system also includes a unit for estimating the components ratio in the resist peeling solution on the basis of the electric conductivity. The resist peeling system further includes a component adding mechanism. The component adding mechanism adds a suitable amount of a component of the resist peeling solution to the resist peeling solution when the electric conductivity monitor estimates that there is an insufficient amount of the component in the resist peeling solution.
The above objects of the present invention are achieved by a method of controlling a resist peeling solution composed of multiple components for peeling resist residue adhering on a semiconductor wafer. In the method, there is monitored the electric conductivity of the resist peeling solution stored in a peeling solution tank. The ratio of the components in the resist peeling solution is estimated on the basis of the electric conductivity. When a component of the resist peeling solution is estimated to be insufficient on the basis of the estimated result, a suitable amount of the insufficient component is added to the resist peeling solution.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.